Dental impression material



Patented Aug. 1, 1933 7 UNITED s'rArEs tense;

DENTA IMPRESSION MAT RIAL Laurence E. Harrison, Long Beach, Calif., as-

signor, by mesne assignments, ,to- Dental 1 Plastics Company, Los Angeles, Calif, a Corporation of California 7 No Drawing. Application June 23, 1930 Serial'No. 463,345

6 iJlaims. (Cris-47) This invention relates to a composition of material suitable foruse by dentists or dental technicians in making impressions of the teeth and gums. More particularly, the invention relates to a material which is adapted to become plastic upon heating or warming to a certain temperar or other material;

' ture and to solidify or. harden upon again cooling, and which is in other respects particularlyadapted for the'making of detailed dental impressions and for the subsequent-molding or casting of reproductions of the teeth and gums with plaster An important object of theinvention is to provide a dental impression material which may be removed from the teeth as an integral body, even in cases in which the teeth are disposed at an angle forming undercuts or inverted wedges in the I impression, such as are sometimes formed bythe it from the mouth and'in other cases it is found 'impossible'to remove the cast without completely destroying the impression. Inthe compound of the present invention thesedis'advantagesare overcom'e by providing the material with a certain amount of elasticity or resiliency, so as to permit it to give or yield when'pulled from the teeth, thus permitting the removal of undercut 7 portions of the impression or of inverted wedges,

and to again return or spring back to the original position of the impression 'aftergit has been re o 1 A further object of the invention is; to provide an impression material; having yielding or resilient properties as above mentioned, and being at the same time adapted to soften or become plastic upon warming to a sufliciently low temperature so as not to burn or hurt the mouth of the patient when placed therein, andto again solidify in' a relatively'short' time, upon chilling, sufiiciently toretain the exact shape of the impression after its removal from the mouth. v

It is' also necessary that the material, in order to "be useful for the above purposegshall have certain other properties. Such material must have sufilcientbody, cohesion, and toughness, so that when squeezed into small crevices and there-= contractionupon chilling, in order to permit a of certain of the ingredients and to facilitate the after chilledit will retain its shape, thus enabling the dentist to'obtain correct detail and measurements of teeth and of their relation to each other. Furthermore, the material must have the proper correct impression tobe obtained.

A further object of the invention isto provide a dental impression material having a-pleasant taste and odor, so that the use thereof is not dieagreeable to the patient.

The material of my invention comprises, in

' general, an intimate mixture comprising the following ingredients:

1. Rubber, preferably pure gum rubber or its equivalent. a i v 2. A solid resinous material adapted to soften or flow upon warming to a relativelylow temperature (about 35 to 55 (3.): and to again solidify upon chilling, such as balata or. gutta percha, or both. r

3. A colloid-forming material, such as gelatine or casein or both.

.4. A finely divided solid lubricant material, such asflaked aluminum, or flaked or powdered graphite.

The mixture preferably also includes small proportions of glycerol and also of solid-oleaginous or waxy material, Such 'oleaginous or waxy material may comprise a fatty acid, such as' stearic acid, whichis solid atordinary temperatures but is adapted'to melt at a relatively low temperature, or a paraffin wax which is solid'at ordinary temperatures but is adapted to melt at 'a relatively low temperature, or both a fatty acid and paraffin wax. The composition also preferably comprises a flavoring or scenting material. The above ingredients are intimately mixed together by milling, and properly controlled heating may advantageously be used at certain stages of this operation in order to soften or melt certain ingredients and facilitate the mixing thereof. Furthermore, a small proportion of. water is preferably added during the milling process in order to prevent excessive drying 00 mixing thereof. In general, a portion of this added Water remains in the final product, and a portion evaporates off during the mixing operation. The final product, therefore, contains only a very small proportion of water. I Y

I have found it advantageous to use certain specific ingredients in certain approximate proportions, as hereinafter described, but it will be understood that the. invention in its broader as- Parts by.

r weight Rubber 30to 50 Fusible resinous material; 60 to 85' Colloid forming material 0030 Finely divided solid lubricant materiah; '10 to40 'Glycerol .4 to .12

Solid oleaginous or waxy "material 10'to To provide the above proportion I of resinous material, I may use either balata or gutta percha or combinations thereof. Toprovide-the above proportion of colloid forming materilalflI' may use from 5 to parts of gelatine and from zero; to 20 parts of casein or glutin. To provide the above mentioned proportion of solid lubricant material I may use from zero to 20 parts by weight of flaked aluminum and from zero to parts by weight of flaked or powdered graphite.

To provide the above mentioned proportion of solid oleaginousor waxy material I may use from 5 to 10 parts'by weight of stearic acid-and from 5 to 10 partsby weight of paraiiin wax; Furthermore, in the making of the material I pre- 81 to add a small proportion of water, say from about'5 to 10 parts by weight, a portion of which may be evaporated during the milling and heats ing process and a portion of which may'remain in the finished material. The material also preferably includes a' small amount, say from] to 2 parts by weight, of flavoring and scenting material, such as methyl salicylate.

I willhowdescribe a specific-embodiment of my invention; "usingwhat I consider to be the preferred specific ingredients and the most ad-' 'vantageous approximate proportions thereof, in

order to provide a materialhaving the optimum combination of the above mentioned desirable properties. The materials used are asfollows: i1

Parts by r l weight Rubber I 40 Ba1ata 72 Gelatine Jc 23 vFlaked aluminum c; 15

Glycerol i ,9

Stearic acid '7 Parafiin' wax .7

.Water 7 Methyl salicylate -1 The above materials are thoroughly and intimately mixed with one another, preferablyby means of milling apparatus such as used, for

example, in the milling or compounding of rub-,

her, and the milling operation may be continued for such length of time as is found necessary for 'this purpose. In general, however, a total millingredients in the formula givenabove, it may be said that all or any desired proportion of the balata may be replaced by an equal proportion of gutta percha. However, I find that balata seems to be fully as satisfactory as gutta percha and is considerably lower in price. The gelatine may be partially replaced by an equal proportion of casein or glutin, butI prefer in any event to use at least five parts of gelatine. Also, in case casein is used in part as the colloid-forming ingredient, I-prefer to also add'a peptizing agent,

.such as boric acid, in the proportion of about 1 part of boric acid to 4 parts of casein, and I also prefer in this case to use a somewhat larger proportion of water than would be the case if gelatine alone were used. In case boric acid is used it also acts as an antiseptic or preservative agent in the composition. The flaked aluminum may alsobe replaced by graphite, but I find that acertain weight of" aluminum is more effective as .a solid lubricant material than the same weight of graphite, so that the weight of graphite used is preferably about twice as great as the aluminum which is replaced thereby in the above formi ila. Another advantage or" the use of aluminum inf-preference to graphite is that it has a higher heat conductivity and thus enables the material to be more quickly softened upon heating a nd to bemore. quickly solidified to the desired'extent throughout, upon chilling.

The'completed material is solid at ordinary temperatures, but has a certain yielding or resilient property which enables impressions formed therefrom to be removed from the teeth under conditions such as above mentioned, even after chilling to atmospheric temperature or below. At such temperatures, however, the material is not. readily susceptibleto permanent deforma tion at ordinary pressures and is adapted to retemperatures the material softens and becomes readily plastic and adapted to flow under pressure and fill all recesses, crevices, and small indentations in the teethand gums when pressed into engagement therewith. A further important property of the material is its ability to chill and solidify quickly throughout after it has been heated to the above-temperatures and the impression has beeri tak'en. This material in its preferred form has a cl illing time, from its fusing or softening temperature to a temperature at which it is adapted toretain its form, of ifrom one to five minutes, upon application of ordinary coldwater of ab0ut'15 to 30? C. thereto. The material also has. a pleasant odoii and taste.

L The method of using this material is, in general, similar'to-the impression materials now in common use. The material ispreferebly softened or rendered'plastic.byplacing a quantity thereof in cold, water, and bringing the water to a boil in about four or five minutes. Thematerial may then be removed from the Water and is sufficiently soft and plastic throughout to permit it to be placed in the usual tray or mold and inserted in the mouth and pressed against the teeth and gums in the usual manner. Atthe time the material is actually inserted in the mouth,-the temperature thereof may, beabout 45 C. or say between 20 and 50 C. The compound is pressed or other material.

firmly into contact with the teeth and gums and is then permitted to cool. The cooling may be facilitated by chilling through application of cold water or cold air to the surface of the impression material, and by this means the material may be cooled sufficiently in about one or five minutes to become sufiiciently solid for removal of the impression. When thematerial is in this condition it is sufiiciently rigid to prevent permanent deformation or loss of shape, provided ordinary care is exercised in removing the same from the mouth, but is still quite resilient, so that it will yield sufiiciently to permit undercut or wedged portions thereof to be readily removed and to then spring back to their original position. Upon further cooling and standing for a period of one hour or more, after removal from the mouth, the material acquires a somewhat more solid and permanent set, so that it may be used for the casting or molding of reproductions in plaster or other material. The material is of such nature as to produce very clean cut reproduction and to produce extremely smooth surface casts in plaster Even in this state, however, the material has a certain amount of resilience and ability to yield, which properly may be advantageous for certain purposes. For example, this permits the impression to be more easily removed from the cast or reproduction formed therewith, so that theimpression may bepreserved for further use. Also, it facilitates removal of the impression from the tray or from the plate of an articulator or other apparatus with which it may be used.

I claim:

1. A dental impression. material consisting principally of rubber and a solid material of a resinous nature similar to b alata and adapted to soften upon warming and to solidify upon chilling, said material also comprising a colloid-forming material and a finely divided solid lubricant material, all of said ingredients being intimately mixed together by milling,and said material containing only a very small proportion of water and having a softening temperature between 35 and 55 C.

2. A dental impression material consisting principally of rubber and balata, and also comprising a colloid-forming material and a finely divided solid lubricant material, all of said ingredients' being intimately mixed together by milling, and said material containing only'a very small proportion of water and having a softening temperature between 35 and 55C.

3. A dental impression material consisting principally of rubber and balata, and also comprising a colloid-forming material, a finely divided solid lubricant material, glycerol, and waxy material, all of said ingredients being integrally mixed together by milling, and said material containing only a-very small proportion of water and having a softening temperature between 35 and 55 C.

4. A dental impression material comprising from to 50 parts by weight of rubber, from 60 to 85 parts by weight of resinous material fusible at a temperature between and 55 C., from 10 to 30 parts by weight of colloid-forming material, from 10 to parts by weight'of finely divided solid lubricant material, from 4 to 12 parts by weight of glycerol, from 10 to 20 parts by weight of solid oleaginous material, and less than 10 parts by weight of water.

5. A dental impression material comprising 40 parts by weight of rubber, '72 parts by weight of balata, 23 parts by weight of gelatine, 15 parts by weight of flaked aluminum, 9 parts by Weight of glycerol, 7 partsby weight of stearic acid, '7 parts by weight of paraflin wax, 7 parts by weight of water, and 1 part by weight of methyl salicylate, all of said proportions being approximate.

6. A dental impression material comprising from 30 to parts by weight of rubber, from to parts by weight of balata, from 10 to 30 parts by weight of colloid-forming material, from 10 to 40 parts by weight of finely divided solid lubricant material, and less than 10 parts by weight of water.

' LAURENCE E. HARRISON. 

